How do I setup a 5 axis mill?

jackotool wrote: Meanwhile, how many parallel ports are required for 5 axis - is one sufficient?

1 if you do not need anything else. It has 12 output pins, 2 for each drive as step/dir, one for enable to all drives and you have one spare for something else. Also it has 5 inputs for 5 limit/home switches.

jackotool wrote: Meanwhile, how many parallel ports are required for 5 axis - is one sufficient?

You can just about get by with one, though spindle control might be tricky.
But if you are building a 5-axis machine I suspect that using a parallel port _at_all_ would be a false economy.

Also, has anyone tried connecting a PCIe parallel port card to a PCIe/PCI adapter - would there be any serious latency issues?

If it works then there will be no significant hardware delay.

One more issue I'm not clear on is operating spindle inside LinuxCNC - I see some people using a RS 485 from VDF to USB and others via a breakout board ...

Please advise what works best and other recommendations ...

Thanks!

RS485 via USB is not realtime. That is not usually a problem with a milling machine, but might not be ideal if running a lathe in CSS mode.

Conversely the RS485 link will give you a lot more feedback from the drive back to LinuxCNC. See the list of pin names here as an example:
linuxcnc.org/docs/2.8/html/man/man1/hy_vfd.1.html